1. Field of the Invention
The present invention generally relates to the field of medical microbiology and immunology. In particular, the invention pertains to an improved vaccine for immunization.
2. Description of the Related Art
Neisseria meningitidis (the meningococcus), identified in 1887 is one of the causative agents of meningococcal meningitis. Twelve subtypes or serogroups of N. meningitidis have been identified and four (N. meningitidis. A, B, C and W-135) are known to cause epidemics. The most common symptoms are stiff neck, high fever, sensitivity to light, confusion, headaches, and vomiting. Even when the disease is diagnosed early and adequate therapy instituted, 5% to 10% of patients die, typically within 24-48 hours of the onset of symptoms. The 10 to 20% of the survivors suffer brain damage, hearing loss, or learning disability. A less common but more severe (often fatal) form of meningococcal disease is meningococcal septicaemia which is characterized by a haemorrhagic rash and rapid circulatory collapse.
Meningococcal bacteria incorporate polysaccharides into their surface structure. Thus a large majority of bacteria are covered with of capsule or glyco-calyx polysaccharide which induces an immunological response in humans. The outer membrane of gram-negative Neisseria meningitidis (NM) bacterium consists, inter alia, of lipopolysaccharide (LPS). Such polysaccharides (PS) are formed on the basis of repeating units in which the constituents and the bonds are defined and which are each characteristics of the NM serogroups defined. These repeating units contain the epitopes which are the antigenicity-determining structures.
The immunogenicity of the capsular polysaccharides to carrier protein can be improved by coupling them to Lipo-oligosaccharides (LOS). When covalently linked to a carrier protein, the resulting PS component in a conjugate vaccine becomes a T cell-dependent (TD) antigen inducing long-term immunity with immune memory even in infants and young children. Further, additional linkage with oligosaccharide (OS) makes a robust conjugate vaccine since OS not only acts as additional immunogen but also as a vaccine adjuvant.